Work underway at the present time is a study of the metabolism, serum protein binding and tissue distribution of 3H-Vitamin D3 in the newborn monkey. Metabolic patterns and tissue distribution at varied times after a single dose is yielding information on the interrelations of protein binding and tissue distribution. An attempt is also being made to purify human serum vitamin D binding globulin in quantity sufficient for characterization of binding properties and development of an immunoassay for same. Partial characterization of the binding capacity of this protein in whole serum (monkey and human) for vitamin D and its various metabolites is also being studied. The eventual goal of the project is to be able to study vitamin D metabolism in infancy and early childhood in such a way as to yield useful data regarding both physiologic and pathophysiologic states.